1. Field of the Invention
The present invention relates to a printed wiring board having a differential signal line and a device including the printed wiring board.
2. Description of the Related Art
A printed wiring board having a thin insulation layer, such as a flexible board, has been used in a device (an electronic device). Japanese Patent Application Laid-Open No. 7-321463 discusses a technology which realizes necessary characteristic impedance by providing a ground line having a mesh shape on a printed wiring board. In this method, capacitance C of the signal line is suppressed without largely narrowing a width of the signal line.
However, Japanese Patent Application Laid-Open No. 7-321463 does not discuss an impedance design considering a connection form of a signal line, e.g., connection of 1 to 1 or 1 to a plurality. In a printed board, various signal lines are connected to a circuit (aboard). A plurality of terminals is provided on the circuit (the board) for connecting other circuits. In such a plurality of terminals, it is conceivable that the terminals include a connection form of 1 to 1 and a connection form of 1 to a plurality. Further, it is also conceivable that in such a plurality of terminals, a connection form of 1 to n and a connection form of 1 to m are included. Further, in such a configuration, if only a signal line of part of connection forms is matched to a termination resistor but a signal line of other connection forms cannot be matched to the termination resistor, reflection of a signal or a wave form distortion occur. As the result of this, a quality of signal transmission to a circuit (a board) decreases.